﻿SEMI0N0TID2E. 
  59 
  

  

  Type. 
  Imperfect 
  trunk, 
  wanting 
  head. 
  

  

  The 
  type 
  species 
  of 
  the 
  so-called 
  Ischypterus, 
  attaining 
  a 
  length 
  

   of 
  about 
  0*2. 
  Trunk 
  regularly 
  fusiform, 
  the 
  depth 
  of 
  the 
  caudal 
  

   pedicle 
  more 
  than 
  one-third 
  as 
  great 
  as 
  the 
  maximum 
  depth 
  of 
  the 
  

   abdominal 
  region. 
  Length 
  of 
  head 
  with 
  opercular 
  apparatus 
  about 
  

   equal 
  to 
  the 
  maximum 
  depth 
  of 
  the 
  trunk, 
  and 
  somewhat 
  more 
  

   than 
  one-quarter 
  of 
  the 
  total 
  length 
  of 
  the 
  fish. 
  Pelvic 
  fins 
  arising 
  

   nearer 
  to 
  the 
  anal 
  than 
  to 
  the 
  pectorals 
  and 
  immediately 
  in 
  advance 
  

   of 
  the 
  dorsal 
  ; 
  anal 
  fin, 
  with 
  seven 
  rays, 
  partly 
  opposed 
  to 
  the 
  

   hinder 
  half 
  of 
  the 
  dorsal. 
  Scales 
  smooth 
  and 
  not 
  serrated, 
  those 
  

   of 
  the 
  middle 
  of 
  the 
  flank 
  scarcely 
  deeper 
  than 
  broad 
  ; 
  dorsal 
  ridge- 
  

   scales 
  acuminate. 
  

  

  Form. 
  <$f 
  Log. 
  Triassic 
  : 
  Massachusetts, 
  Connecticut, 
  and 
  New 
  

   Jersey, 
  U.S.A. 
  

  

  P. 
  1036. 
  Imperfect 
  fish 
  ; 
  Durham, 
  Connecticut. 
  Egerton 
  Coll. 
  

  

  P. 
  1035. 
  Pish 
  with 
  well-preserved 
  squamation; 
  Boonton, 
  New 
  

   Jersey. 
  Egerton 
  Coll. 
  

  

  P. 
  3511. 
  Impression 
  of 
  trunk 
  apparently 
  deepened 
  by 
  distortion 
  

   in 
  the 
  abdominal 
  region; 
  Massachusetts. 
  

  

  Enniskillen 
  Coll. 
  

  

  P. 
  1017 
  a, 
  b. 
  Two 
  small 
  specimens, 
  one 
  wanting 
  head, 
  the 
  other 
  

   wanting 
  caudal 
  region 
  ; 
  Sunderland, 
  Mass. 
  Egerton 
  Coll. 
  

  

  P. 
  3511 
  a. 
  Fragmentary 
  remains, 
  probably 
  of 
  this 
  species 
  ; 
  Sunder- 
  

   land. 
  EnnisJcillen 
  Coll. 
  

  

  Semionotus 
  tenuiceps 
  (Agassiz). 
  

  

  1835-36. 
  Eurynotus 
  tenuiceps, 
  L. 
  Agassiz, 
  Poiss. 
  Foss. 
  vol. 
  ii. 
  pt. 
  i. 
  

  

  pp. 
  159, 
  303, 
  pi. 
  xiv 
  c. 
  figs. 
  4, 
  5. 
  

   1837. 
  Palceoniscus 
  lotus, 
  J. 
  H. 
  Eedfield, 
  Ann. 
  Lyceum 
  Nat. 
  Hist. 
  New 
  

  

  York, 
  vol. 
  iv. 
  p. 
  38, 
  pi. 
  ii. 
  

   1837. 
  Eurynotus 
  tenuiceps, 
  J. 
  H. 
  Eedfield, 
  ibid. 
  p. 
  39. 
  

   1841. 
  Palceoniscus 
  latus, 
  W. 
  C. 
  Eedfield, 
  Amer. 
  Journ. 
  Sci. 
  vol. 
  xli. 
  

  

  p. 
  25. 
  

   1841. 
  Eurynotus 
  tenuiceps, 
  E. 
  Hitchcock, 
  Geol. 
  Massachusetts, 
  vol. 
  ii. 
  

  

  p. 
  459, 
  pi. 
  xxix. 
  figs. 
  1, 
  2. 
  

   1850. 
  Ischypterus 
  latus, 
  Sir 
  P. 
  Egerton, 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  vi. 
  

  

  p. 
  10. 
  

   1857. 
  Eurinotus 
  ceratocephalus, 
  E. 
  Emmons, 
  Amer. 
  Geology, 
  pt. 
  6, 
  

  

  p. 
  144, 
  pi. 
  ix 
  a. 
  

   1860. 
  Eurinotus 
  ceratocephalus, 
  E. 
  Emmons, 
  Man. 
  Geology, 
  ed. 
  2, 
  

  

  p. 
  188, 
  fig. 
  164. 
  

  

  